Electrostatic application of solid lubricants

ABSTRACT

This disclosure describes an apparatus for applying a solid lubricant to the working surface of forge tools. Gas pressure forces the particles through an electrostatic charging chamber wherein the particles receive an electrostatic charge. The charged particles are emitted from a nozzle onto the working surface of the forge tool being lubricated. Because the working surface is formed of a material of opposite electrostatic charge, the charged particles adhere to the surface. An electrostatic coil may be mounted inside of the forge tool to oppositely charge the tool and aid in the application of the lubricant. The electrostatic coil also maintains an attractive effect between the charged particles and the tool when the forge tool is heated to a point where its surface loses its ferromagnetic properties.

United States Patent a corporation of Delaware ELECTROSTATIC APPLICATION OF SOLID LUBRICANTS 4 Claims, 2 Drawing Figs.

U.S. Cl 184/1, 117/17, 118/62, 184/6 Int. Cl ..Fl6n 15/02, BOSb 5/02 Field of Search 184/1 E, 6;

Primary Examiner-Manuel A. Antonakas AlI0rrly-Gl'lff1n, Branigan, Truex, Seemar & Kindness ABSTRACT: This disclosure describes an apparatus for applying a solid lubricant to the working surface of forge tools. Gas pressure forces the particles through an electrostatic charging chamber wherein the particles receive an electrostatic charge. The charged particles are emitted from a nozzle onto the working surface of the forge tool being lubricated. Because the working surface is formed of a material of opposite electrostatic charge, the charged particles adhere to the surface. An electrostatic coil may be mounted inside of the forge tool to oppositely charge the tool and aid in the application of the lubricant. The electrostatic coil also maintains an attractive effect between the charged particles and the tool when the forge tool is heated to a point where its surface loses its ferromagnetic properties.

TO POTENTIAL SUPPLY I l9 23 i l! CHARGED PARTICLES sou D LUBRICANT s PARTICLES n ha PATENTEDJANIQIBYI I 35561255 T0 POTENTIAL SUPPLY CHARGED PARTICLES souo LUBRICANT S PARTICLES INVENTOR Ggprge F. Lomox,dn

. m fal ATTORNEYS ELECTROSTATIC APPLICATION OF SOLID LUBRICANTS BACKGROUND OF THE INVENTION Most forging operations, whether hot or cold. require that the forge tools be coated with a lubricant. In the past. the hot forge industry practice has been to coat the forge tools with a compound that basically consists of a graphite powder suspended in a hydrocarbon oil base liquid carrier. Upon application to hot tools, the liquid carrier provides an adhesive quality that aids in coating the surface of the tool with the suspended graphite. Although the oil burns upon contact with the hot surface, the cokelike residue is sufficiently impregnated with the graphite powder to provide lubrication during the following forgingoperations.

While the foregoing practice has found widespread use. it has not been entirely satisfactory. Specifically, the combustion of the oil when it impinges on the hot tools produces a sooty smoke. The smoke contains graphite particles that are released from the compound during the combustion process. These particles of combustion permeate the atmosphere in the forge area and constitute a health hazard to operating person nel. In addition, the products of combustion contaminate the surrounding equipment, especially electrical apparatus such as hydraulic pump drive motors.

More recently, attempts have been made to use water as the liquid carrier so as to reduce the health hazard and the contamination of the surrounding equipment. While this ap proach shows great promise in reducing the contamination of the forge area atmosphere, the sudden vaporization of the water upon contact with the hot tool surfaces releases a portion of the entrained graphite particles. Hence, while combustion products are eliminated, the atmosphere is still contaminated by graphite particles.

Therefore, it is an object of this invention to provide a new and improved apparatus for applying a dry lubricant to forge tools that does not contaminate the atmosphere and does not constitute a health hazard to operating personnel.

It is a further object of this invention to provide a new and improved apparatus for applying a solid'particle dry lubricant to forge tools that does not generate combustion products and does not release sufficient particles to contaminate the air and create a health hazard.

SUMMARY OF THE INVENTION In accordance with a principle of this invention an apparatus for applying dry lubricant particles to forge tools is provided. Particles of a dry lubricant, such as graphite, are forced through an electrostatic charging means, In the electrostatic charging means the particles receive an electrostatic charge; thereafter, the particles are forced through a spray nozzle. The spray nozzle is directed toward the tool whose surface is to be coated with the lubricant.

In accordance with a further principle of the invention an electrostatic charging chamber is coupled through a supply line to a source of solid lubricant particles. And, the solid lubricant particles are forced through the supply line by gas pressure, for example.

In accordance with a further principle of the invention an oppositely charged (to the charge of the particles) means such as an electrostatic coil is mounted inside of the working surface of the forge tool to aid in the application of the particles to the work surface of the forge tool. In addition, the electrostatic coil aids in retaining the charged particles on the surface of the tool when the tool is in use.

From the foregoing description of the invention it will be appreciated that an uncomplicated apparatus for coating a forge tool with solid lubricant particles is provided. The particles are charged by an electrostatic source and sprayed through a spray nozzle onto the surface of the tool. Because oil is not used as an adhesion agent, there are no combustion products generated when the particles impinge on the surface of the tool even though the tool is hot. In addition, because water is not used as an adhesion agent. sputtering does not occur when the particles impinge on the surface of the tool. Hence, none of the detrimental effects of the prior art apparatus for coating a tool with a dry lubricant result from the use of the apparatus of the invention. That is, because a carrior material is not necessary, the detrimental effects of the prior art are eliminated. In addition, when the tool is oppo'sitm ly charged by a coil or other means mounted in the tool, a wraparound effect occurs. This wraparound effect results in a uniform coating with little or no blowby or particle drift.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying'drawings wherein:

FIG. I is a pictorial diagram illustrating the invention: and

FIG. 2 is a cross-sectional diagram ofa forge tool illustrating an electrostatic coil mounted in the tool.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I is a schematic diagram illustrating the invention and comprises: a source of solid lubricant particles 11; an electrostatic charging chamber 13; and a nozzle 15. The source of solid lubricant particles 11 is connected to a gas supply 18 by a line [7. The source of solid lubricant particles 11 is also connected to the electrostatic charging chamber 13 by a.solid lubricant particle supply line 19. The electrostatic charging chamber 13 is connected to a potential supply by a line 21. The nozzle is located on the opposite side of the electrostatic charging chamber from the solid lubricant particle supply line 19. Hence, the particles pass directly through the chamber. Located in front of the discharge end of the nozzle 15 is a tool 23 whose surface is to be coated by the solid lubricant particles.

In operation. the gas supply supplies a gas that flows through the solid lubricant particle container 11, entrains or entraps the particles, and carries the particles out the solid lubricant particle supply line 19. These particles then pass into the electrostatic charging chamber 13 which induces an electrostatic charge.

The charged particles, which are still under pressure, are sprayed by the nozzle 15 onto the surface of the forge tool 23. The nozzle provides a direction of flow and a particle velocity sufficiently high to assure a lubricant stream that will cover the intended tool target. While it is not essential to the basic operation of the invention, it is preferred that the target tool include means for inducing an electrostatic charge of the opposite polarity to the charge of the particles. This opposite charge insures that the particles are captured by the tool and held. In addition, the interaction of the oppositely charged electrostatic fields permits unidirectional application of the lubricant with wraparound uniform thickness of the solid particle deposits. That is, the dual charges provide for uniform thickness of lubricant without the target (tool) having to be revolved or moved in front of the nozzle.

FIG. 2 illustrates an apparatus for generating an electrostatic charge inside of a tool target. Illustrated in FIG. 2 is an outer tool shell 31 having a cooling water shell 33 mounted immediately adjacent to the inner side of the tool shell 31. It will be appreciated by those skilled in the art that cooling water jackets are typical in hot forge tools. Mounted inside of the cooling water jacket 33 is an electrostatic coil 35 wound around a coil support 37. The built-in cooling water jacket, in addition to its usual beneficial effects, also thermally protects the coil. Iiy applying a current to the electrostatic coil 35 an electrostatic charge is developed on the surface of the tool. If the tool charge is opposite to the charge of the particles, the particles are attracted to the tool and the above-mentioned wraparound effect occurs.

It will be appreciated from the foregoing that the invention provides an apparatus for applying solid lubricant particles to a forge tool. The particles may be graphite, plastic or any other solid lubricant particles that will accept an electrostatic charge. The particles are charged in a charging chamber and directed by a nozzle onto the surface of the tool. Preferably, an electrostatic charge of opposite polarity is created on the tool. This charge attracts the particles so that they uniformly adhere to the surface of the tool. While the tool charge aids in the application ofthe charged particles to the tool surface, it is not essential to the invention. In addition, while the tool charge creating means can be removed from the tool after the particles have adhered to the surface of the tool, it does not have to be removed. In fact. ifthe tool is to be utilized in a hot forging operation, it is preferred that the charging means not be removed because the exterior surface of the tool can rise to temperatures wherein the tools ferromagnetic properties are reduced. If this reduction occurs, the particles tend to drop away from the tool. However, if the coil is maintained in the tool and is maintained energized, the tool remains charged so that the particles remain adhered to the tool. Hence, in certain environments it is preferable to maintain an energized electrostatic coil or other charge creating means in the tool while the tool is being used in a forge operation.

It will be appreciated by those skilled in the art and others that the foregoing has described a preferred embodiment of the invention; however, other embodiments fall within the scope of the invention. For example, other apparatus than a coil may be utilized inside of the tool to provide a charge that will attract the charged particles. In addition, while the invention has been described as using a gas to provide the flow of particles into the electrostatic charging chamber, it will be appreciated that various gases can be used; the only limitation on the gas is that it must have a low moisture content. For example, dry air can be utilized. Alternatively, nitrogen or other inert gases can be used. Moreover, other means of conveyance such as centrifugal impellers which do not require gas to impart velocity may be used.

It will be further appreciated that, while the invention finds its greatest use in coating hot forge tools with lubricant particles When they are hot. it can also be used in other environments. For example. the invention can be used to coat cold forge tools with lubricant particles. Also, the invention can be used to coat hot forge tools when they are cold.

I claim:

1. Apparatus for applying dry, solid lubricant particles onto the work surface ofa forge tool comprising:

a source of dry, solid lubricant particles:

particle movement means coupled to said source of dry.

solid lubricant particles for moving said particles;

an electrostatic charging chamber connected to said source of dry, solid lubricant particles so as to receive said particles;

said electrostatic charging chamber adapted to apply an electrostatic charge to the particles received by said chamber from said source ofdry, solid lubricant particles;

a nozzle connected to the output of said electrostatic charging chamber for dispensing said charged particles onto the work surface ofa forge tool; and,

means mounted in said forge tool for applying an electrostatic charge to the work surface of said forge tool opposite in polarity to the charge applied to said particles by said electrostatic charging chamber.

2. Apparatus for applying dry, solid lubricant particles to the work surface of a forge tool as claimed in claim 1 wherein said means for applying a charge to the work surface of said tool comprises an electrostatic coil mounted in said tool.

3. Apparatus for applying dry, solid lubricant particles onto the work surface of a forge tool as claimed in claim 2 wherein said particle movement means comprises a source of dry gas under pressure.

4. Apparatus for applying dry, solid lubricant particles onto the work surface of a forge tool as claimed in claim 3 where said particles are graphite. 

1. Apparatus for applying dry, solid lubricant particles onto the work surface of a forge tool comprising: a source of dry, solid lubricant particles; particle movement means coupled to said source of dry, solid lubricant particles for moving said particles; an electrostatic charging chamber connected to said source of dry, solid lubricant particles so as to receive said particles; said electrostatic charging chamber adapted to apply an electrostatic charge to the particles received by said chamber from said source of dry, solid lubricant particles; a nozzle connected to the output of said electrostatic charging chamber for dispensing said charged particles onto the work surface of a forge tool; and, means mounted in said forge tool for applying an electrostatic charge to the work surface of said forge tool opposite in polarity to the charge applied to said particles by said electrostatic charging chamber.
 2. Apparatus for applying dry, solid lubricant particles to the work surface of a forge tool as claimed in claim 1 wherein said means for applying a charge to the work surface of said tool comprises an electrostatic coil mounted in said tool.
 3. Apparatus for applying dry, solid lubricant particles onto the work surface of a forge tool as claimed in claim 2 wherein said particle movement means comprises a source of dry gas under pressure.
 4. Apparatus for applying dry, solid lubricant particles onto the work surface of a forge tool as claimed in claim 3 where said particles are graphite. 